The instant invention is predicated upon the world's need for materials which possess a range of characteristics not present in naturally-occuring materials. Only through the synthetic engineering of uniquely propertied materials, can technological progress be freed from the constraints previously imposed by such natural materials. The basis for the innovation discussed hereinafter is the destruction of these constraints which, until recently, had led to relatively limited usable ranges of thermal, electrical, optical, structural and chemical characteristics obtainable from any single one of such natural materials. Now that the constraints of nature's symmetry have been destroyed, the fabrication of materials having nonstoichiometric compositions, unique orbital configurations and variant bonding becomes possible. Such deviant compositions and configuration provide for the synthesis of new materials which emphasize unlimited combinations of desired properties.
The essence of the present invention is to provide a process by which to fabricate synthetic materials which are thereby particularly tailored to accomplish any desired task. In order to accomplish such an ambitious goal, it is necessary to introduce component species which have been excited to an energetic state into the host matrix of a base material by a novel fabrication process in which the synthetically engineered electronic and chemical bonding configurations of those species in that host matrix are altered and permanently preserved. It should be noted that the term "component" or "component material" as used herein refers to any species which participates in the interactions leading to the final synthetically engineered material, regardless of whether that species is physically present in the final product. Components can include inter-alia, inert gases or other species which transfer energy to, or otherwise influence the formation of the material.
One set of methods for the fabrication of synthetic materials, which prior art synthetic materials are characterized by a range of chemical, optical, thermal, electrical and physical properties (albeit a limited range) not present in naturally occurring materials, has previously been described in "rapid quenching" literature. By rapidly quenching precursor material from a non-solid state, certain non-equilibrium states and local bonding orders characteristic of the precursor material state can be preserved in the quenched state. In contrast, the same precursor material, more slowly cooled from a non-solid to a solid state, will form a material which does not exhibit the non-equilibrium states and local bonding orders possible for the rapidly quenched material. Typically, the non-equilibrium state material produced by rapid quenching will contain at least some phases characterized by disordered, amorphous, microcrystalline, or polycrystalline structures, with possible crystalline inclusions. Since the properties of the materials produced by rapid quenching are different from those of slowly cooled materials, high quench rate processes have found commercial application in the production of bulk and thin film amorphous and disordered materials exhibiting desirable, novel properties.
Rapid quench techniques have heretofore been used to incorporate one or more "modifying" elements into the host matrix of a preselected material, thereby providing for the possible alteration of one or more of the physical, chemical, thermal, electrical or optical properties of that host material in a preselected manner. Hopefully, said alteration could be accomplished without adversely affecting other properties which, in naturally occurring or unmodified materials, are seemingly interrelated to and dependent upon the altered properties. This principle will be referred to hereinafter as "modification". In other words, modification will be defined, for purposes of the instant invention, as the introduction of a modifying species into the host matrix of a precursor material for the purpose of uncoupling otherwise interrelated properties of that host matrix material. In the preferred definition, and as detailed hereinafter, modification will affect at least the electronic configurations of the host matrix material.
While rapid quenching has been discussed hereinabove, it is to be noted that various other methods are available by by which modifying elements or species can be added to the host matrix of a precursor material. For instance, modified amorphous materials have heretofore been made by, e.g. thin film processes, chemical vapor deposition, sputtering and cosputtering, glow discharge, and microwave glow discharge. These methods of modification, the modified materials obtained thereby and the unique properties attained by modification are described in, for example, U.S. Pat. No. 4,177,473 to Stanford R. Ovshinsky for Amorphous Semiconductor Member and Method of Making the Same; U.S. Pat. No. 4,177,474 Stanford R. Ovshinsky for High Temperature Amorphous Semiconductor Member and Method of Making the Same; U.S. Pat. No. 4,178,415 to Stanford R. Ovshinsky and Krishna Sapru for Modified Amorphous Semiconductors and Method of Making the Same; U.S. Pat. No. 4,217,374 to Stanford R. Ovshinsky and Masatsuga Izu for Amorphous Semiconductors Equivalent to Crystalline Semiconductors Produced by a Glow Discharge Process; and U.S. Pat. No. 4,520,039 to Stanford R. Ovshinsky for Compositionally Varied Materials and Methods for Synthesizing the Materials.
The modified materials disclosed in the aforementioned patents are formed in a solid amorphous host matrix having structural configurations which have local rather than long range order. In a like manner and according to the principles disclosed therein, a modifier species may be added to the host matrix of the precursor material, said species having orbitals which interact with the orbitals of the host matrix. This interaction results in the substantial modification of the electronic configurations of the host matrix of the precursor material. The materials produced as a result of said orbital interaction have, on the atomic or microscopic level, atomic configurations which have been substantially changed to provide, e.g., independently increased electrical conductivity without corresponding changes in thermal conductivity. The resultant materials exhibit both chemical and structural modification, both type of modification resulting in properties characteristic of non-equilibrium materials with modified local orders, structures and configurations.
Of particular interest relative to the instant invention is a disclosure relating to the modification of the host matrix of precursor materials by melt spinning process, said disclosure found in U.S. Pat. No. 4,339,255 to Stanford R. Ovshinsky and Richard A. Flasck for Method and Apparatus for Making a Modified Amorphous Glass Material (said patent assigned to the assignee of the instant invention). This '255 patent describes a method and apparatus for introducing a fluidic modifier into a host matrix, said fluidic modifier optionally containing one or more active gases, such as oxygen, nitrogen, silicon tetrafluoride, or arsine. The synthetic materials made by the disclosed process can be metallic, dielectric, or semiconductor modified amorphous glass materials. The modified synthetic materials can range from alloys, to materials with varying degrees of alloying and modification, to materials in which only modification and doping actions exist. While the '255 patented method provides for the modifier species to be incorporated at various intervals or layers, at different rates and in different sequences; the number of species incorporated, the number and interval of layers and the rates and sequence of introduction are limited.
It is noteworthy that through the utilization of the method described in U.S. Pat. No. 4,339,255 it is even possible to produce modified ceramic materials, i.e., ceramic materials exhibiting properties not naturally occurring in normally prepared material. Also, since the interaction between the modifier material and the precursor material from which the host matrix is formed does not take place in a crucible where the materials are liquidified, but rather on the surface of a melt spinning chill wheel, the material thereby produced can be of a composite structure, of a modulated structure, or even of a layered structure.
While the method disclosed in U.S. Pat. No. 4,339,255 does permit the fabrication of modified ceramic materials, the process utilized to make the resultant material is that of melt spinning onto the peripheral surface of a chill wheel. As described hereinabove, melt spinning is a rapid quench process and can have quench rates as high as 10.sup.8 degrees Centigrade per second. However, melt spinning is actually one of the slower rapid quench techniques, especially when compared to more rapid techniques such as sputtering. Therefore, it has heretofore not been possible to produce modified bulk materials at the higher range of quench rates. it would, of course, be desirable (for production purposes, as well as for the fabrication of the highest quality modified materials) to fabricate modified bulk materials at very high quench rates, since the resultant materials would be characterized by a range of properties unobtainable because of the lower quench rate limitations of melt spun processes.
Therefore, the instant invention relates to innovative fabrication techniques for the synthesis of novel classes of modified materials, which techniques do not sulfur from any of the limitations imposed by the Flasck '255 process or by any other of the heretofore developed rapid quench processes. More particularly, the Flasck '255 process is limited to the fabrication of relatively thin film materials, to the formation of a limited number (one, two or three) of layers of those thin film materials and to a single host matrix precursor material in each layer thereof. The '255 process also does not provide for the use of a core member upon which is deposit those modified thin film materials.
Additionally, while the '255 patent does disclose the fabrication of modified dielectric materials, the melt spinning process used therein permits only a rather limited rate of diffusion of the modifier species into the host matrix. Thus, it is not possible to use the method disclosed in that patent to fabricate one class of extremely useful materials, the class of ceramic materials whose properties are modified on an atomic level. Such "atomic ceramics" may exhibit combinations of properties heretofore unknown in nature or in conventionally or exotically fabricated analogs.
In contrast to said heretofore developed rapid quench processes, the instant invention provides for the fabrication of synthetically engineered materials having a liquified metallic, semiconductor or ceramic host matrix into which energetic modifying elements are introduced. Due to the fact that the fabrication process of the instant invention may be repeatably cycled with a variety of host matrix precursors, successively deposited layers of the host matrix may be repeatedly changed with the same modifier or sequentially changed with varying modifiers to develop either a multilayered, compositionally varied body of bulk material or a single homogenous body of bulk material which can be built to relatively thick dimensions. Also, the modified material may be deposited upon an externally engineered core member which is drawn through a series of deposition stations. Finally, because the process of the instant invention requires the interaction of the host matrix of the precursor material and the modifier material to occur during exposure to the atmosphere and while the modifier material is maintained in an activated state, both high quench rates and high diffusion rates are obtained. By incorporating the energetic modifier species into the host matrix at high diffusion rates, it becomes possible to fabricate a truly atomically alloyed ceramic material.
These and other objects and advantages of the instant invention will becomes apparent from the drawings, the detailed description and the claims which follow.